Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$73.55	5.551%	$77.6328	$77.63	$77.65	$77.60
Purchase #2	$246.59	11.684%	$275.4016	$275.40	$275.40	$275.40
Purchase #3	$48.34	3.718%	$50.1373	$50.14	$50.15	$50.10
Purchase #4	$94.70	10.723%	$104.8547	$104.85	$104.85	$104.90
Purchase #5	$73.35	13.826%	$83.4914	$83.49	$83.50	$83.50
Purchase #6	$232.68	13.682%	$264.5153	$264.52	$264.50	$264.50
Purchase #7	$162.85	7.319%	$174.769	$174.77	$174.75	$174.80
7 purchase totals =	$932.06		$1,030.8021	$1,030.80	$1,030.80	$1,030.80